Meaning
Analytical diagnostic techniques evaluate the voltage decay rate across a cell following current interruption. Measuring differential voltage relaxation reveals phase transitions, lithium diffusion behavior, and internal equilibrium dynamics within electrode materials. The technique isolates kinetic decay rates over extended open-circuit relaxation periods.
Scope limits cover post-current equilibrium tracking without extending to continuous load spectroscopy.
Thermodynamic Probe
Voltage response curves derivative with respect to time display distinct peak features corresponding to phase changes. Analyzing differential voltage relaxation identifies state-of-charge dependent equilibrium shifts within composite intercalation electrodes. Solid-solution regions show rapid relaxation profiles compared to two-phase coexistence zones.
Internal concentration gradients dissipate during the observation window. Kinetic peak shifts correlate with structural phase transition boundaries.
Degradation Diagnostic
Degradation mechanism tracking relies on changes in relaxation peak positions and magnitudes over cycle life. Aging increases differential voltage relaxation times due to thickened solid electrolyte interphase layers and lost active material. Comparison between fresh and aged cells quantifies internal diffusion resistance growth.
Non-destructive testing provides insights into internal cell health without disassembly.
Data Acquisition
High-resolution voltage logging equipment records potential decay at millisecond sample intervals. Computing numerical derivatives generates differential voltage relaxation curves. Temperature control ensures reproducible relaxation measurements across testing protocols.
